When Ar-Adûnakhôr became King, he took his name in Adûnaic. He was the first of the Kings of Númenor to do this; although most of the Númenóreans had stopped using the Elven tongues generations before, it was still customary for the Kings to take their royal names in Quenya. This break with tradition, along with the very meaning of the name itself (Adûnakhôr signifed "Lord of the West" and properly referred to Manwë the Elder King) antagonized those of the Númenóreans who were still loyal to the Valar (called the Faithful). To the Faithful, the choosing of this name represented outright blasphemy and a direct challenge to the rightful leadership of the Valar.

In addition to taking an Adûnaic name, Ar-Adûnakhôr forbade the speaking of the Elven tongues in his presence. Because of the cold feelings of Ar-Adûnakhôr and most of his people to the Eldar and the Valar, Elven ships came from Tol Eressëa to the west of Númenor only seldom and in secret.

Had Ar-Adûnakhôr taken a Quenya name, he would have ruled as Tar-Herunúmen.